Masking and purging mutations following EMS treatment in haploid, diploid and tetraploid yeast (Saccharomyces cerevisiae)
Masking and purging mutations following EMS treatment in haploid, diploid and tetraploid yeast (Saccharomyces cerevisiae)
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DOI：
10.1017/s0016672300004821
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发表时间：
2001-02-01
影响因子：
1.5
通讯作者：
Otto, SP
中科院分区：
文献类型：
--
作者：
Mable, BK;Otto, SP
酵母，酿酒酵母，被用作研究倍性进化理论的模型。使用烷化剂EMS（乙烷甲基磺酸盐）进行诱变实验，以评估有害突变的掩蔽对DNA损伤的响应和恢复的相对重要性。特别是，我们测试了具有较高倍性水平的细胞在诱变后是否具有相对较高的适合度，掩蔽的优点在四倍体中是否比在二倍体中更明显，以及清除突变是否允许比具有较高倍性水平的细胞更快地恢复单倍体细胞。使用（1）原养型单倍体（MAT α）和二倍体（MAT α/α）菌株和（2）缺乏功能性交配型基因座的等基因单倍体、二倍体和四倍体菌株，对无性繁殖的稳定期细胞进行单独的实验。在这两组实验中，单倍体表现出比二倍体更明显的表观生长速率下降，但单倍体和二倍体似乎都恢复得非常快。四倍体没有表现出增加的好处相比，与二倍体掩蔽，但体积测量和FACScan分析营养缺陷型菌株表明，所有处理的四倍体菌株倍性水平下降，一些处理的单倍体线倍性水平增加。来自这些实验的结果证实，虽然掩蔽有害突变在诱变剂存在下为较高倍性水平提供了直接优势，但选择在去除诱导突变方面极其有效，导致生长速率在所有倍性水平下随时间迅速增加。此外，在EMS存在下，倍性水平本身是一种可变性状，单倍体和四倍体通常都向二倍体进化（S.在实验过程中，
The yeast, Saccharomyces cerevisiae, was used as a model to investigate theories of ploidy evolution. Mutagenesis experiments using the alkylating agent EMS (ethane methyl sulphonate) were conducted to assess the relative importance that masking of deleterious mutations has on response to and recovery from DNA damage. In particular, we tested whether cells with higher ploidy levels have relatively higher fitnesses after mutagenesis, whether the advantages of masking are more pronounced in tetraploids than in diploids, and whether purging of mutations allows more rapid recovery of haploid cells than cells with higher ploidy levels. Separate experiments were performed on asexually propagating stationary phase cells using (1) prototrophic haploid (MAT alpha) and diploid (MATa/alpha) strains and (2) isogenic haploid, diploid and tetraploid strains lacking a functional mating type locus. In both sets of experiments, haploids showed a more pronounced decrease in apparent growth rate than diploids, but both haploids and diploids appeared to recover very rapidly. Tetraploids did not show increased benefits of masking compared with diploids but volume measurements and FACScan analyses on the auxotrophic strains indicated that all treated tetraploid strains decreased in ploidy level and that some of the treated haploid lines increased in ploidy level. Results from these experiments confirm that while masking deleterious mutations provides an immediate advantage to higher ploidy levels in the presence of mutagens, selection is extremely efficient at removing induced mutations, leading growth rates to increase rapidly over time at all ploidy levels. Furthermore, ploidy level is itself a mutable trait in the presence of EMS, with both haploids and tetraploids often evolving towards diploidy (the ancestral state of S. cerevisiae) during the course of the experiment.